The present invention relates generally to control systems, and more specifically to control systems that use event logs for diagnostic purposes.
Because of the possibility of power outages, many businesses, data centers and other entities use battery backup systems to ensure that electrical power will be available for critical items even if a utility outage occurs. One technology that has been developed to avoid power outages is the Uninterruptible Power Supplies (UPS). A UPS typically includes a battery providing reserve electrical power if a main source of electrical power fails. Thus, if utility power fails, electric services can continue as long as the UPS device provides sufficient battery power to supply the needed electricity.
A variety of different techniques have been used to improve reliability and/or capacity of UPS systems. The techniques include a serial redundant arrangement. A typical serial redundant arrangement involves, for example, first and second UPSs connected in a serial fashion wherein, in a first mode of operation, the first UPS is bypassed while the second UPS is serving the load and, in a second mode of operation, the second UPS is bypassed while the first UPS serves the load, such that the first and second UPSs may serve as standby backups for one another.
Typically, a serial redundant arrangement of UPS systems includes an embedded UPS controller configured to control UPSs. The UPS controller typically compiles all detected errors and other significant events in an event log. When the UPS system is serviced, for example, after some problem or failure, the event log can be examined to help determine the cause of the problem or failure. One standard form of event log is a “circular” event log. Once the event log is full, new events overwrite the oldest events in the log. This does not work well for events that trigger a cascade of error events. If there are enough follow-on events, the trigger event(s) could be discarded and unavailable for diagnoses. The likelihood of unavailable events of interest can be reduced by using event logs with greater capacity. However, embedded UPS controller's integrated-circuit real estate is limited so that it is not practical to use an event log that is large enough to store all possible events of interest. These utilities do not provide a flexible way to capture and retain events of greatest interest at appropriate granularity level.